This application claims the priority benefit of Japanese applications serial no. 2002-247201, filed on Aug. 27, 2002; serial no. 2002-247204, filed on Aug. 27, 2002; serial no. 2002-250927, filed on Aug. 29, 2002.
1. Field of the Invention
The present invention relates to a multi-stage compression type rotary compressor comprising an electrical-power element arranged within a sealed vessel, a first and a second rotary compression element that is driven by the rotary shaft of the electrical-power element, wherein the refrigerant compressed by the first rotary compression element is compressed by the second rotary compression element, and the refrigerant gas compressed and discharged by the first rotary compression element is sucked to the second rotary compression element and is compressed and discharged thereby. The present invention also relates to a setting method of displacement volume ratio for the multi-stage compression type rotary compressor.
2. Description of the Related Art
A conventional rotary compressor sucks the refrigerant gas to the low-pressure chamber side of a cylinder through a suction port of the rotary compression element. The refrigerant gas compressed by the operations of a roller and a vane is temporarily discharged into the sealed vessel through the discharge port at the high-pressure chamber side of the cylinder and then is discharged to outside through the sealed vessel. The vane is installed movably in a groove formed in a radial direction of the cylinder. The vane is pressed against the roller to divide an inside of the cylinder into a low-pressure chamber side and a high-pressure chamber side. A spring is provided on a rear side of the vane to urge this vane on a roller side. A back pressure chamber that communicates with the sealed vessel is set within the groove for urging the vane on the roller side. Therefore, the high-pressure inside the sealed vessel is charged to the back pressure chamber and urges the vane on the roller side.
In this rotary compressor, the application of refrigerant with combustibility, such as propane (R290), HC refrigerant excluding Freon has been considered due to the damage of the ozone layer resulting from Freon refrigerant.
It is necessary to make the sealing amount of the combustible refrigerant such as, a propane in low amount, due to the security consideration. The security limitation for propane serving as refrigerant is 150 g. However, it is necessary to limit the sealing amount to be 100 g for sufficient security in practice (50 g for refrigerator using).
Because the refrigerant is discharged after being compressed in the sealed vessel in the rotary compressor, the sealed volume of the refrigerant must be in excess of 30 g xcx9c50 g compared to the refrigerant in a reciprocating compressor with the same volume as the rotary compressor. Therefore, the regulatory stringent regarding to the use of the rotary compressor with combustible refrigerant.
The conventional multi-stage compression type rotary compressor, as shown in FIG. 13, sucks the refrigerant gas to the low-pressure chamber side of the cylinder 240 through the suction port 262 of the first rotary compression element 232. The refrigerant gas is compressed to a medium pressure by operations of the roller 248 and the vane 252 and is discharged through the discharge port 272 at the high-pressure chamber side of the cylinder 240. Therefore, the medium pressure refrigerant gas is sucked to the low-pressure chamber side of the cylinder 238 through the suction port 261 of the second rotary compression element 234. The second compression of the refrigerant gas is done by the operations of the roller 246 and the vane 250 to make the refrigerant have high temperature and high pressure, and the refrigerant is then discharged through the discharge port 270 at the high-pressure chamber side. The refrigerant discharged by the compressor flows into a radiator. After the refrigerant has been radiated, it is closed in the expansion valve and then is heat-absorbed by the evaporator and sucked to the first rotary compression element 232. This cycle is repeated. Furthermore, in FIG. 13, the reference numeral 216 indicates a rotary shaft of the electrical-power element. The reference numerals 227, 228 indicate discharge valves set inside the discharge-muffler chamber 262, 264 to open or close the discharge ports 270, 272.
The displacement volume of the second rotary compression element 234 is set smaller than that of the first rotary compression element 232. Under this condition, in the conventional rotary compressor, the thickness (height) of the cylinder 240 of the first rotary compression element 232 is made smaller than that of the cylinder 238 of the second rotary compression element 234; the internal diameter of the cylinder 238 of the second rotary compression element 234 is made smaller than that of the cylinder 240 of the first rotary compression element 232; the eccentric amount of the roller 246 of the second rotary compression element 234 is made small (the external diameter of the roller 246 is made large). By doing so, the displacement volume of the second rotary compression element 234 is set to be smaller that of the first rotary compression element 232.
It is to be discussed that the use of the combustible refrigerant that exerts medium pressure in the sealed vessel in the multi-stage compression type rotary compressor. The pressure inside the sealed vessel is relatively low compared to the high pressure refrigerant gas discharged into the sealed vessel. In other words, because the low pressure refrigerant has low density, the amount of the refrigerant existing in the sealed vessel can be reduced. Especially, in the case when the ratio of displacement volume of the second rotary compression element to the first rotary compression element is large, the medium pressure is difficult to rise. Therefore, the amount of the refrigerant that is sealed within the sealed vessel can be further reduced.
However, in a case when the medium pressure is lowered in the sealed vessel in the rotary compressor, during the start-up of the compressor, the pressure inside the sealed vessel that serves as a back pressure and is charged to the vane of the first rotary compression element is difficult to rise, this may break away the vanes.
Moreover, because it takes time in the internal medium-pressure compressor to reach a balanced pressure after the rotary compressor stops, the startability of re-start-up is poor.
The displacement volume ratio of the multi-stage compression type rotary compressor has suitable values according to the various usages. For each suitable value, parts must be replaced (including the changing of the material type, working equipment and measuring instrument, etc.) in the eccentric amount of the rotary shaft, the external diameter of the roller or the internal diameterxc2x7height of the cylinder. Moreover, due to the difference of the eccentric amount of the rotary shaft between the first rotary compression element and the second rotary compression element, the working of the rotary shaft is divided into more steps.
Thus, the manufacturing time that is spent on replacing parts becomes longer, and the cost (including the cost on change of the material type, working equipment and measuring instrument, etc.) due to the changing or replacements of parts becomes high.
The present invention resolves the problems caused by the conventional rotary compressor. An object of the present invention is to prevent unstable movements such as breakaway of the vane in the internal medium-pressure, multi-stage compression type rotary compressor using combustible refrigerant. It is another object of the present invention to improve the startability of the compressor.
Moreover, still another object of the present invention is to provide a multi-stage compression type rotary compressor and a setting method of displacement volume ratio thereof. In the compressor, the cost can be lowered, the workability can be improved and the optimum displacement volume ratio can be easily set.
Another object of the present invention is to provide a multi-stage compression type rotary compressor that uses combustible refrigerant as refrigerant. The refrigerant that has been compressed by the first rotary compression element is discharged to the sealed vessel. The discharged medium pressure refrigerant is compressed by the second rotary compression element. Therefore, the pressure inside the sealed vessel becomes medium pressure. The gas density of the refrigerant that is discharged to the sealed vessel becomes low.
Another object of the present is to provide a multi-stage compression type rotary compressor, wherein the displacement volume ratio of the second rotary compression element to the first rotary compression element is set large.
Yet another object of the present invention is to provide a multi-stage compression type rotary compressor, wherein the displacement volume ratio of the second rotary compression element to the first rotary compression element is not less than 60%. The medium pressure that is compressed by the first rotary compression element is limited. Therefore, the gas density of the refrigerant inside the sealed vessel can be lowered. The pressure is relative low compared to an internal high-pressure, single-stage compression type compressor. Therefore, the amount of refrigerant melted into oil can also be lowered.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor, wherein the displacement volume ratio of the second rotary compression element to the first rotary compression element is not less than 60% and not more than 90%. Therefore, the unstable operation of the first rotary compression element can be prevented, and the gas density of the refrigerant that is discharged to the sealed vessel can be lowered.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor, wherein the volume ratio of the space where the refrigerant exists to the volume of the sealed vessel is not less than 60%. Therefore, the existing space of the refrigerant gas inside the sealed vessel becomes small, and the amount of sealed refrigerant can be lowered.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor, wherein the first and second cylinders constructing the first and second rotary compression elements, the first and second support members that block each opening face of the cylinders and serves also as a bearing for the rotary shaft, and intermediate partition plates that are arranged between cylinders are shaped close to the inner surface of the sealed vessel. Therefore, the existing space of the refrigerant gas in the sealed vessel can be efficiently lessened, and the amount of sealed refrigerant and oil can be remarkably lowered.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor comprising: the first and second cylinders constructing the first and second rotary compression elements, the first and second rollers that rotates eccentrically with eccentric portions formed on the rotary shaft of the electrical-power element, the first and the second vanes that are in contact with rollers to divide each cylinder into a low-pressure chamber side and a high-pressure chamber side, and the first and second back pressure chambers for constantly urging each vane towards the roller side. A combustible refrigerant is applied as a refrigerant. The refrigerant that has been compressed by the first rotary compression element is discharged to the sealed vessel. The discharged medium pressure refrigerant gas is compressed by the second rotary compression element. At the same time, the discharging side of the refrigerant in the second rotary compression element is connected to the first and second back pressure chambers. Therefore, the high pressure refrigerant gas that has been compressed by the second rotary compression element is charged into the first and second back pressure chambers.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor comprising: a support member that blocks the opening face of the second cylinder, a discharge-muffler chamber formed in the support member for discharging the refrigerant that has been compressed in the second cylinder, a communication path formed in the support member and communicating with the discharge-muffler chamber and the second back pressure chamber, an intermediate partition plate arranged between the first and second cylinders, and a communication hole formed in the intermediate partition plate for communicating with the second and first back pressure chambers. Therefore, the high-pressure at the discharging side of the refrigerant in the second rotary compression element can be charged into the first and second back pressure chambers with a relatively simple structure.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor comprising: a pressure equalizing passage that communicates with the discharge-muffler chamber and the sealed vessel, and a pressure equalizing valve that opens or closes the pressure equalizing passage. The pressure equalizing valve opens the pressure equalizing passage when the pressure inside the discharge-muffler chamber is lower than that inside the sealed vessel. Therefore, the pressure within the first and second rotary compression elements and the sealed vessel can be rapidly equalized.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor using a combustible refrigerant, wherein the refrigerant that has been compressed by the first rotary compression element is discharged to the sealed vessel. The medium pressure refrigerant that has been discharged is compressed by the second rotary compression element. The compressor comprises a pressure equalizing valve that communicates with the discharging side of the refrigerant in the second rotary compression element and the sealed vessel in the case when the pressure at the discharging side of the refrigerant in the second rotary compression element is lower than the pressure inside the sealed vessel. Thus, after the compressor stops, the pressure within the sealed vessel can be rapidly equalized.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor comprising: a cylinder that constructs the second rotary compression element, a support member that blocks the opening face of the cylinder, a discharge-muffler chamber formed in the support member and discharging the refrigerant that has been compressed in the cylinder, a cover that divides the discharge-muffler chamber and the sealed vessel, and a pressure equalizing passage formed in the cover. The pressure equalizing valve is arranged inside the discharge-muffler chamber to open or close the pressure equalizing passage. Therefore, the structure of the compressor is simplified and the efficiency of space-usage can be improved.
Still another object of the present invention is to provide a multi-stage compression type rotary compressor, wherein the dimensions of the first and second eccentric portions are same, and the dimensions of the first and second rollers are same, and the dimensions of the first and second cylinders are same. The second cylinder extends outwardly with a predetermined angle range in the rotation direction of the second roller from the suction port. Therefore, the starting of the compression of the refrigerant in the cylinder of the second rotary compression element becomes delayed.
Still another object of the present invention is to provide a setting method of displacement volume ratio for the multi-stage compression type rotary compressor. The method comprises: extending the second cylinder outwardly with a predetermined angle range in the rotation direction of the second roller from the suction port; setting the displacement volume ratio of the first and second rotary compression elements by adjusting the compression-starting-angle. Therefore, the starting of the compression of the refrigerant in the cylinder in the second rotary compression element can be delayed. The displacement volume of the second rotary compression element can be lowered.